Investigation of Corrosion Protection Systems for Bridge Stay Cables. Corrosion211 Protection for Post-Tension Tendons and Cable Stay Systems

摘要

The use of cable-stayed bridges in medium- and long-span applications in the211u001eUnited States has increased significantly in the past ten years. Of paramount 211u001eimportance with this type of bridge is the protection of the stay cables from 211u001ecorrosive elements. An extensive survey, reported herein, showed a general 211u001econcern over the adequacy of the corrosion protection of the most widely used 211u001ecurrent system. In this study the popular two-barrier system (prestressing strand 211u001einside polyethylene sheath injected with portland cement grout) was examined 211u001eexperimentally. The effectiveness of the grout in providing secondary corrosion 211u001eprotection in the event of a cut or break in the external sheathing was a major 211u001efocus of the experimental work. Such breaks have been documented on a US bridge. 211u001eSmall-scale experimental studies were conducted to develop a low-bleed grout for 211u001euse in the large-scale stay tests. In addition, small-scale accelerated corrosion 211u001etests were conducted on grouts containing corrosion inhibiting admixtures. The 211u001emajor portion of the experimental program involved accelerated durability testing 211u001eof eight large-scale stay cable specimens. Each stay specimen was 9.5-m long and 211u001ewas composed of 12 12.7-mm diameter 7-wire prestressing strand. The inclined stay 211u001especimens were stressed to bridge dead load levels and then injected with the low-211u001ebleed portland cement grout. Additional axial and lateral loads were then applied 211u001eto most specimens to simulate field loading conditions.